Once upon a time, England's third richest man shocked the world by admitting he was suffering from depression. "About eight years ago I hit the buffers – it came totally out of the blue. One day, I woke up and couldn't get out of bed. I thought, OK, I'll be better tomorrow, but the next day was even worse. I couldn't face the world, couldn't handle social interactions of any sort. At that moment, all my wealth counted for nothing. I was fragile and, although never suicidal, I recognised something was desperately wrong and I needed to do something fast."

And that is how the Duke of Westminster came to take three months off in order to recover from a major depressive breakdown. Would that other men could be so well-advised or in a position to finance the opportunity.

By and large, men wouldn't touch such a confession with a barge pole. It seems to me there's a paradox in the depression literature, suggesting that while women provide the greatest symptomology of self-dislike, low self-esteem, pessimistic and negative personal thinking, leading to classical self-harming behaviours, men suffer from equally severe emotional problems. With exceptions such as the noble Duke, they just don't talk about them.

The official position is that currently one in six adults is depressed and women are twice as likely as men to get the diagnosis. But a report launched from the United Kingdom Council for Psychotherapy (UKCP) via the London School for Economics shows that the way organisations such as the National Institute for Health and Clinical Excellence (Nice) collect depression statistics is likely to under-calculate the totals for men.

At present, Nice employs a system called the "Quality of Life Years" method (Qaly). This relies on patients basically guessing how bad various illnesses might be if they were to contract them, an approach that critics claim is both dated and misrepresentative. (It gives rise to the joke that since some people think certain illnesses are "worse than death" the best way to improve the patient's Qaly statistic would be to kill them.)

The more modern "Subjective Well-being" method measures what actually happens to patients when they fall ill. These alternative calculations not only show that depression is 10 times worse than any other illness bar none, they also highlight how male depressives might manage to disappear from the data.

Today the NHS will tell you roughly 3-4 per cent of men have depression as against 7-8 per cent of women. But it's acknowledged that men are far less likely to seek medical help for their condition. In all cases, women out-use the health service compared with men, from puberty to age 75. Doctors are less likely to diagnose men with depression. And because of male "bravado" under the Qaly system, those who play down the existence of the problem and the severity of symptoms will automatically get a cleaner bill of health in their statistical result.

Does it matter? The UKCP report indicates that depression is not only the "worst illness in the world" because it traps you in "a prison without a door" (to borrow from psychologist Dorothy Rowe), it also costs you six times as much as the next most serious illness in terms of lost well-being. For precise values, a serious case of clinical depression will reduce quality of life by the equivalent of £44,237 each year as opposed to £5,556 each year for kidney trouble.

As a very broad generalisation, men show their depressions differently from women. In America, it is already accepted that drug and alcohol abuse by men represents clinical evidence of depression. Men – tellingly – are twice as likely as women to suffer from alcoholism. I contend that the national depression statistics for men would be very much altered if we factored in the consequences of excessive stress, drinking and drug abuse plus male workaholism and road rage. It helps to recall that some depression is agitated and noisy instead of silent and glum. Not convinced? Why, then, are men half as likely as women to be diagnosed with depression, but three times more likely than women to kill themselves because of it?